


You don't want to go up there, I promise!

by Library_Drone



Category: Fallout (Video Games), Fallout 3, Undertale (Video Game)
Genre: Crossover, Gen, Non-Chronological, Violence, everyone at some point probably - Freeform, gender neutral pronoun frisk, mild descriptions of gore, more tags to come
Language: English
Status: In-Progress
Published: 2017-07-15
Updated: 2018-01-14
Packaged: 2018-12-02 10:43:49
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 7
Words: 2,421
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11507757
Author URL: https://archiveofourown.org/users/Library_Drone/pseuds/Library_Drone
Summary: It's been 200 years and change since a human last fell down. The world is different now. Dead and dangerous. Frisk doesn't understand why the monsters want to leave so badly when here the food and water is rad free and nothing is trying to eat you, but the monsters insist on leaving. Frisk has to warn them.They can't go up there. The Wasteland will eat them alive.





	1. a would be mother blocks the way!

**Author's Note:**

> I have not been able to get the idea of a Fallout crossover with Undertale out of my head. be warned that isn't a kind world that Frisk comes from and this will affect their behavior. The chapters will be non-linear and the plot will be loose indeed. I hope you all enjoy these stories and if you have any ideas or suggestions feel free to let me know. I'm always interested.

     Frisk stepped back from the tall monster that blocked their way, peering up at her through raggedly cut bangs.  The wall of white fur and purple cloth was as intimidating as any _real_ monster frisk had ever seen. The furred woman had been kind to them, Frisk had appreciated that, but they could tell that Toriel hadn't seen _Frisk_ when she looked at them. Instead she had only seen echoes of whomever those toys, those shoes, that small bed had originally belonged to.

 

     “You wish to know how to return "home," do you not? Ahead of us lies the end of the RUINS. A one-way exit to the rest of the underground. I am going to destroy it. No one will ever be able to leave again. Now be a good child and go upstairs.”

 

     Frisk didn’t blame her for that, there were plenty of people they’d met who’d lost someone. Everyone loses someone before too long. But there was always that niggling paranoia of more being lost someday. It _was_ a little weird how attached the monster woman had gotten already. But until now it hadn’t felt particularly _threatening_.

 

_I never called you mom. I’m a child but I’m not yours. But I could’ve stayed. I wanted to but…_

 

They didn’t want to go home. But they couldn’t stay here right now.

 

“Every human that falls down here meets the same fate. I have seen it again and again. They come. They leave. They die. You naive child... If you leave the RUINS... They... ASGORE... Will kill you. I am only protecting you, do you understand? ... go to your room.

Do not try to stop me. This is your final warning.”

_Oh Toriel._ Frisk thought. _Everyone dies. The whole world wants to kill you and everyone you love. And most of the time it succeeds. You can’t hide from the world. And I’m harder to kill than you think._

 

“You want to leave so badly?”

 

No, they didn’t want to leave at all.

 

 “Hmph.  You are just like the others. There is only one solution to this. Prove yourself... Prove to me you are strong enough to survive.”

 

Frisk had survived this long, but they wished it didn’t need to end this way.

The whole world would kill these monsters, these people.

_Sorry Toriel, but… I HAVE TO WARN THEM!_


	2. the pen and the hand are mighty indeed

**Summary for the Chapter:**

> Chapter 2 here! 
> 
> While there's plenty of evidence in the game that reading and writing are far from uncommon skills in the wasteland, I figure sign language would be one of those things that get lost in a nuclear apocalypse.

Frisk didn’t talk much as a rule. They didn’t talk at all if they could avoid it, and this could (and did) lead to problems when forced into contact with other people. Maybe things were easier Pre-war for the mute, but these days…. yeah most people could read (if not very well) but good luck finding blank paper to write on or tools to write with.  And it took too long anyway. Makes it hard to hold a conversation.

(besides, people tend to shoot at strangers outside of safe encampments)

So when the taller (LOUDER) of the two skeleton brothers gave Frisk a crisp clean pad of paper and a pack of pencils –

“BECAUSE THE GREAT PAPYRUS WILL ALWAYS TAKE THE TIME TO LISTEN TO HIS FRIENDS! ”

\--Well, if Frisk had to sniff a few times, the cold could be blamed. Absolutely.

 And when the other one (short, lazy, a little scary) pulled them aside and gesturing oddly while saying-

“hey kid. noticed you don’t say much yeah? that’s fine, you do good with what you got. Seems like you got plenty to say. all that writing looks like whole lotta work though. so how ‘bout i teach you Hands? could let you chat a lot faster and i dunno how many humans understand it, but most monsters do.”

-Frisk thinks they could be forgiven for tackling the him into the snow (and for the damp spot the spread across the front of his shirt).

He spreads his fingerbones over the back of their head and ruffles their already messy hair, chuckling.

“yeah. that’s what I thought.”

 

 


	3. observing a new variable

**Summary for the Chapter:**

> Sans gets his first look at frisk. and doesn't quite know what to think.

 

Sentry duty wasn’t exactly the most riveting job in the world, but it paid in gold to keep him and his bro housed and fed. And in quality naps.

Sans was lounging in the upper boughs of a tree settling in for his 10 am snooze when something that never happened…happened. With a long low grown of unused hinges and the gringing of gravel, the enormous purple doors at the end of the Snowedin caverns- the ones that had been sealed shut scince before sans had ever been BORN—slowly swung open. Sans slowly sat up on the branch, peering into the snow to get a good look at what wandered out of those long lost parts of the underground. It was…a kid?

The figure that walked out of the ruins (door swiftly slamming shut behind them) was in stripes all right. Their sweater was a dingy, ragged thing of faded pink and blue. Oversized, torn, and dirty looking, the thing was in way worse shape than anything a parent would let their kid run around in. (even with the increasing scarcity of useable items washing down into the dump) There was an equally ragged bag strapped to their shoulders and a wicked looking **_knife_** of all things strapped to their leg. The flesh they could see was strangely sallow nad the kids looked thin in an unhealthy sort of way. Not that their weren’t monsters naturally rail thin, but it look natural on the kid.

But, the more he looked… yeah this kid wasn’t a monster. It was a _human_.

A human. This could be bad. The kid was dirty enough that he couldn’t tell if it just had a lot of dust on them, or if the was _Dust_ in the mix. It kept pausing to scan the area with their heavily squinted eyes. Tilting their head this way and that. Searching. As if it could sense him watching. It shivered a bit while poking curiously at the snow drifts with its toes.

An armed human… heading towards papyrus. Towards his whole reason to get out of bed some days. Towards a town of innocent monsters.

Well… Sans would just have to introduce himself now wouldn’t he?


	4. to herald the end of all things

**Summary for the Chapter:**

> Warning for some mild-ish description of blood and gore. nothing graphic really but still

“why are you so determined to get to asgore kid?”

 

Frisk glanced at their skeletal friend. The two of them stood in the golden hall before the throne room, alone. There was traces of dust on their ragged clothing, on their fists, in their hair, but strangely not on the knife strapped to their thin calf.

 

“you don’t got much by the way of killing intent, but still you’ll kill monsters. you don’t seem to want to leave. but you struggle on to the end on the underground. what is it you want form the king?”

 

They hated Sans’ judging gaze. But for all that the skeleton was more practical, suspicious, and generally world wise than any monster they had spoken to… the judgment in that stare proved that what they were doing was the right thing. Not even Sans was ready for the Capital Wasteland. They’d met five year olds better prepared than most of these monsters.

 

‘It’s for their own good’ Frisk signs at him. Their gestures are sharp, and somewhat frantic. _My hands isn’t good enough yet._ Pausing, they write the rest.

 

‘The Wasteland would RUIN them Sans. If Asgore only needs one more soul to break the barrier then I HAVE to make him understand that the barrier should never be broken. There’s nothing out there for monsters but death and pain. There’s nothing for _humans_ even.’

 

They remembered raiders. The screamed curses, the squishing noise of spilled innards. The thundering of rifles and the slick wet slide of blood, they remembered. They remembered hiding under the rusted-out shell of a car as the remaining _animals_ dug through her mothers’ bags.

 

_They remembered._

 

‘The sky isn’t worth giving this up.’


	5. Bathing in poison is bad for your skin

Waterfall was going to kill them.

Frisks’ skin was crawling with fear as they looked into caves ahead. The drip-drop-drip sound of water echoed around them in a steady beat that was familiar as the diner cave Up in Little lamplight. It could almost have almost been comforting if it wasn't for the fact that it was going to kill them.

So much was _glowing_.

Glowing things were bad. Always. If it wasn’t a lamp and it put of light it was a slow painful poison. And Frisk wasn’t exactly swimming in Rad-Away and Rad-X right now.

A bit of a poem their mom had once read to them passed through their mind as they stood at the mouth of Waterfall. “You won’t have much time, / radiation poisoning is a drag / The survival clock is ticking, / countdown to a body bag”

     Frisk had a half dose or Rad-X stuffed away in their backpack. Enough for an emergency if something unexpected came up, but they hadn’t had to think about randomly running into places with high radiation output in a long time. Everybody knew what areas to avoid in Little-Lamplight so it was usually enough. But they didn’t know how long these caves went on (Monsters lived in there? Did that mean they were Rad proof? That’s be useful.) and they didn’t know how high of a rad output the glowing stuff gave off. (High if they had to guess though. Had to be if they could see the light from here.)

     They were going to die. Or become a ghoul which would be worse. A child ghoul, They’d never get any bigger right? Ghouls didn’t age/ Could kids even become ghouls? They shuddered as they pictured their skin peeling up, losing their hair, losing their NOSE….

 _Stop being morbid._ They thought to themselves. Glancing behind themselves to where they had left Papyrus they steeled their SOUL.

     And started to run.

**Notes for the Chapter:**

> To someone who grew up in the wasteland, Waterfall would be anything but beautiful. 
> 
> The bit of poem in this is a snippet from Just In Case by Freddie Robinson


	6. Dogs and Dust

**Notes for the Chapter:**

> flashing forward in the timeline quite a bit, Frisk and a team of monsters scout the surface for the first time. It doesn't end well.

This situation was _exactly_ the kind of thing that Frisk had been afraid of. Innocent souls even less prepared for the hardships of the wastes than the relatively sheltered kids of Little Lamplight.

They’d tried to prepare the monsters of the Underground for what lurked in the harsh light of the sun.

Never assume someone was a friend.

Never approach a stranger. Or a strange animal.

Always prepared for a fight.

     These were the first rules of the Wastes.  They’d given the monsters a rundown of the more common forms of life and sources of death out in the wastes, hoping to make them understand what they were in for. The monsters though…

     They’d seen the state of the children of little Lamplight. The near starvation and the way the other kids watched the residents of the underground with wary, if curious eyes. Frisk didn’t think they’d been taken truly seriously. The monsters looked sad for them but they didn’t look like they understood.

     Most of the monsters were staying close to Little Lamplight for now, but Frisk had a few with them scouting the surrounding areas. Undyne, The Dog Squad, and (despite Frisks arguments) Sans and Papyrus were all coming along. Most of these choices would have been…not fine, because Frisk still doesn't want the monsters exposed out here, but alright. Even Sans was an ok choice, for all of his fragility. Papyrus though…

     Papyrus was strong, there was no arguing that. He’d stomped Frisk flat more than once underground. Papyrus was clever, confident, and skilled. Those were all great survival skills. But Papyrus was also kind, generous, and believed the best of everyone even when it was beyond reason to do that.

Papyrus believed that everyone could be a good person if they just tried. He didn’t understand that a lot of people _wouldn’t try._

Mercy is Papyrus’s only option, he wouldn’t finish things.

Frisk understood that urge, but it just wasn’t practical. Not up here.

     So, when the pack of wasteland mongrels leap out of the dark to attack the small party it was bad. So bad. Blood, marrow and Dust coated the ground as the monsters engaged with the pack. Through the snapshot awareness of blood and teeth Frisk saw papyrus go down, the alpha dog snapping at his neck.

And then, knife flashing, Frisk was there. And the dogs weren't. And Greater Dog wheezed on the ground. And Undyne bled. And Sans, unhurt stares at them with his eye glowing bright.

_Drip drip drip_

 They were alright

      They hoped.


	7. A flower a day

**Summary for the Chapter:**

> Flowey's first time meeting Frisk

“In this world it’s _KILL or BE KILLED_! “

Flowey warped his malleable face into as creepy and intimidating a shape as he could manage. The line was delivered with perfect timing. Just the right amount of cheerful speech just before. Deepening and warping his voice for that little bit of extra oomph competed the effect.

It was a good face, He’d had a loooong time to practice after all.

But the new human looked… Unfazed.

They stood staring at him placidly. Eyes slightly wider than the perpetual squint they had been wearing before but otherwise…

Barely a twitch.

He noticed the other child kept their hand close to their pants pocket. Ready for something. But they didn’t seem afraid at all. Maybe they needed some encouragement.

“Didn’t you hear me you idiot?! You’re going to die! Or become a murderer! That’s the way this world works! You won’t escape it! No one does. You’ll Die down here like all the others!”

He paused for a moment. Waiting. Then opened his mouth again to –

“Yeah?” The word was quiet. Almost inaudible. A rasped strangely. Like the kid hadn’t spoken in a long time.

“What do you mean _YEAH_?” He spat.

The kid shrugged lightly but otherwise didn’t move. They kept their eyes on him. Watching.

“Yeah? And?” the dirty child repeated with a slow, hesitant cadence.

“AND? Doesn’t that make you _scared_? Doesn’t that make you **ANGRY**? They’re all going to try to kill you!” he shrieked, letting loose a unhinged sounding cackle. That should shake them a bit. He hoped so.

The kid hesitated before speaking again. They almost choked on the words.  “Wh-why would it? I mean. That is how things work. I m-m-mean everywhere. Everything and everybody is always tr-trying to kill you. Th-that isn’t new”

They reached a hand into the pocket. Seeming to fiddle with something. He wondered what it was.

“But that doesn’t mean I have to play along” they continued. “Maybe I’ll die… that’s how my folks went. But I’ll die knowing I was good”

Flowey tossed one last insult, with accompanying sneer before burrowing back into the cool dirt.

At least this one wouldn't be boring.


End file.
